We note here that the equation (REF ) may, alternatively, be solved by the iteration method [1]}, [2]}, [3]}, [4]}. Although this procedure is accurate for large values of \(Q^2/\Lambda ^2\)  when \(a(Q^2/\Lambda ^2)\)  is small, it violates the analytical attributes of \(a(Q^2/\Lambda ^2)\)  near the point \(Q^2/\Lambda ^2 = 1\)  [5]}. The present approach is consistent with the requirement of analyticity and thus is
convenient to investigate further the analytical properties of the causal coupling \(\bar{\alpha }_t(Q^2/\Lambda ^2)\) .
